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The groundwater level (GWL) is a significant foundation design factor that often fluctuates with seasonal variations, causing a reduction in the strength and stiffness of submerged soil mass and resulting in an additional settlement that affects the structural performance of foundations. Pore water pressure (PWP) changes with the water level, and the excess pore water pressure (EPWP) changes during the loading stages. The pore water pressure (PWP) and excess pore water pressure (EPWP) variations were studied under full saturation with relative density (Dr: 50%, 75%, and 95%) and fluctuating groundwater levels, monitored through two piezometer sensors placed at 1B and 2B below the base of foundation (where the B=width of foundation). The experiments included loading rectangular and square footings on top of poorly graded sand. The results in full saturation indicated that the increase in the relative density of the sand only slightly increased the amount of PWP generations, though with a more noticeable impact on the EPWP with the time required for the EPWP to reach its maximum value range between 3 to 10 minutes in the majority of the results. In the fluctuating groundwater levels, the decrease in the water table below the base of the footings decreased the amount of pressure. [ABSTRACT FROM AUTHOR]

This research focuses on investigating the bearing capacity and settlement of dry sandy soil by the use of physical modelling tests involving the loading of the surface of the foundation on the dry sand with various relative densities (Dr=50, 75, 95). The results indicated that increasing the relative density multiplies the obtained bearing capacities. In general, the load-settlement curves showed non-linear behaviour for the sand, indicating that the settlement of the footing increased with increasing the applied loading until failure occurred. Increasing the relative density from 50% to 75% and from 75% to 95% increased the bearing capacity by about 50% in each case. For the failure mechanism of both footings with dense and very dense sand, general shear failure with total rupture of the soil was observed, and a local shear failure was observed for the sand with medium relative density. [ABSTRACT FROM AUTHOR]